﻿using System;
using System.Diagnostics;
using Windows.ApplicationModel;
using Windows.ApplicationModel.Activation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Navigation;
using Xamarin.Forms;
using Application = Windows.UI.Xaml.Application;
using Frame = Windows.UI.Xaml.Controls.Frame;

namespace PagesGallery.UWP
{
	/// <summary>
	/// Provides application-specific behavior to supplement the default Application class.
	/// </summary>
	partial class App : Application
	{
		/// <summary>
		/// Initializes the singleton application object.  This is the first line of authored code
		/// executed, and as such is the logical equivalent of main() or WinMain().
		/// </summary>
		public App()
		{
			InitializeComponent();
			Suspending += OnSuspending;
		}

		/// <summary>
		/// Invoked when the application is launched normally by the end user.  Other entry points
		/// will be used such as when the application is launched to open a specific file.
		/// </summary>
		/// <param name="e">Details about the launch request and process.</param>
		protected override void OnLaunched(LaunchActivatedEventArgs e)
		{
#if DEBUG
			if (Debugger.IsAttached)
				DebugSettings.EnableFrameRateCounter = true;
#endif

			var rootFrame = Window.Current.Content as Frame;

			// Do not repeat app initialization when the Window already has content,
			// just ensure that the window is active
			if (rootFrame == null)
			{
				// Create a Frame to act as the navigation context and navigate to the first page
				rootFrame = new Frame();

				rootFrame.NavigationFailed += OnNavigationFailed;

				Forms.Init(e);

				if (e.PreviousExecutionState == ApplicationExecutionState.Terminated)
				{
					//TODO: Load state from previously suspended application
				}

				// Place the frame in the current Window
				Window.Current.Content = rootFrame;
			}

			if (rootFrame.Content == null)
			{
				// When the navigation stack isn't restored navigate to the first page,
				// configuring the new page by passing required information as a navigation
				// parameter
				rootFrame.Navigate(typeof (MainPage), e.Arguments);
			}
			// Ensure the current window is active
			Window.Current.Activate();
		}

		/// <summary>
		/// Invoked when Navigation to a certain page fails
		/// </summary>
		/// <param name="sender">The Frame which failed navigation</param>
		/// <param name="e">Details about the navigation failure</param>
		void OnNavigationFailed(object sender, NavigationFailedEventArgs e)
		{
			throw new Exception("Failed to load Page " + e.SourcePageType.FullName);
		}

		/// <summary>
		/// Invoked when application execution is being suspended.  Application state is saved
		/// without knowing whether the application will be terminated or resumed with the contents
		/// of memory still intact.
		/// </summary>
		/// <param name="sender">The source of the suspend request.</param>
		/// <param name="e">Details about the suspend request.</param>
		void OnSuspending(object sender, SuspendingEventArgs e)
		{
			var deferral = e.SuspendingOperation.GetDeferral();
			//TODO: Save application state and stop any background activity
			deferral.Complete();
		}
	}
}